Interactions of cells with each other and with extracellular materials are critically important in embryonic development and in the maintenance of adult form and function. Our objective is to determine how cell surface glycoproteins involved in cell adhesion produce morphogenetic changes during Drosophila development. P93 is a 93 kD 20-hydroxyecdysone dependent cell surface glycoprotein. Antibodies specific for P93 have been produced, and the cDNA for the gene for P93 has been cloned. We propose to sequence this cDNA to deduce amino acid sequence of P93. P93 appears to be identical to the 92 kD component of the PS (position specific)3 antigen. The PS 1 and PS2 antigens have been shown to be Drosophila integrins. In embryos, P93 appears to play a role in cell formation and in muscle attachments. We propose to determine if P93 is associated with other cell surface or with cytoskeleton associated proteins during embryogenesis. High resolution immunolocalization of P93 in embryos will be done to identify ultrastructural localization(s) and to determine subcellular structures with which P93 may interact. These studies should increase our understanding of the mechanisms through which adhesion proteins produce specific changes in cell behavior which cause morphogenesis in animal tissues.